I've thought about this. What seems likely is that we are born as organisms with no ideas about self or about anything else - just mammals hanging out in direct experience. Then the illusion must be spun by some combination of social conditioning / expectation and language. Young babies don't understand a thing, and yet their brains are able to discern patterns and learn. Because our parents made the same noises when performing actions that affect what's in our experience, we must have constructed an ego to serve as the thing that those noises refer to. And as we grow in our cultures that emphasise intellect instead of emotion, experience, physical experience, we begin to experience the world as basically words and concepts. And we are praised for doing so!Was there a "self" at birth?
If not, how did the illusion, the story, develop & when?
When did the story develop? I dont' know. But all my earliest memories, going back at least as far to age 3, are all loaded with ideas of subject and object - with a very real-feeling "me" as the subject. Could be that procedural memory (muscle memory, emotional memory) has no place for self the same way it has no place for any concept, image, or word.
I'm running away with this. I hope I'm addressing the heart of your question.

